What year?  Mileage?  How is car usually driven?

Is that one wheel hotter than the one on the other side or are they both
equally hot?  If one is hotter, then that caliper is probalby not releasing
properly.  It probably has been going on for a while and you wore through
the brake pad and you are getting backing plate on rotor scraping noises.
Your caliper may have seized up, your brake hose has an obstruction or
the hose may have collapsed.  You should start by pulling the wheel and
checking the pad.  Based on what you see, you can continue the diagnosis.
---------------
Alex

I had the same problem a while back. I checked back there
and found a brake owl (Teves hootii) perched on my axle.
He had wedged his high-friction plumage against the disk on
the inside, and was furiously clawing at the calipers.

I fed him a mouse and all was well.

Hope this helps.

Or, just maybe, it might be a sticking piston in the caliper,
allowing the pad to continually rub against the disk, creating
both the screeching and generating heat.  Dirt/debris can
sometimes get in places, and prevents the piston from retracting
sufficiently, which keeps the pad in contact with the disk
instead of properly freeing it.  Or the pad could have become
misaligned; same results.  Or maybe you ain't got no pad
no more, since it wore out, and you're being treated to the
song of metal-on-metal, soon to be superceded by the
symphony of brake repair.